JAJSIM1 February 2020 LM60430 , LM60440
ADVANCE INFORMATION for pre-production products; subject to change without notice.
The output voltage of the LM604x0is externally adjustable using a resistor divider network. The range of recommended output voltage is found in the Recommended Operating Conditions table. The divider network is comprised of RFBT and RFBB, and closes the loop between the output voltage and the converter. The converter regulates the output voltage by holding the voltage on the FB pin equal to the internal reference voltage, VREF. The resistance of the divider is a compromise between excessive noise pick-up and excessive loading of the output. Smaller values of resistance reduce noise sensitivity but also reduce the light-load efficiency. The recommended value for RFBT is 100 kΩ; with a maximum value of 1 MΩ. If a 1 MΩ is selected for RFBT, then a feedforward capacitor must be used across this resistor to provide adequate loop phase margin (see CFF Selection). Once RFBT is selected, Equation 3 is used to select RFBB. VREF is nominally 1 V (see the Electrical Characteristics for limits).
For this 5-V example, RFBT = 100 kΩ and RFBB = 24.9 kΩ are chosen.